High in the San Juan Mountains of Colorado, tourists in search of an old-time thrill can ride a coal-fired train to the historic mining town of Silverton, visit the 12-ton marble Christ of the Mines Shrine, and honor the local tradition of enthusiastic drinking. (“Sunday is not generally observed save by increased guzzling,” the Silverton Democrat wrote in 1884.) But outside Silverton lies another legacy of mining—one far quieter, and more treacherous, than a gold-rush saloon.

In the surrounding steep valleys, hundreds of defunct silver and gold mines pock the slopes with log-framed portals and piles of waste rock. When water flows over the exposed, mineral-laden rock in and around the mines, it dissolves zinc, cadmium, lead, and other metals. The contaminated water, sometimes becoming acidic enough to burn skin, then dumps into nearby streams. So-called acid mine drainage, most of it from abandoned boom-time relics, pollutes an estimated 12,000 miles of streams throughout the West—about 40 percent of western waterways.

Near Silverton, the problem became bad enough to galvanize landowners, miners, environmentalists, and local officials into a volunteer effort to address the drainage—work that has helped avert a federal Superfund designation and restore a gold-medal trout population downstream. With a few relatively simple and inexpensive fixes, such as concrete plugs for mine portals and artificial wetlands that absorb mine waste, the Silverton volunteers say they could further reduce the amount of acid mine drainage flowing into local rivers. “In some cases, it would be simple enough just to go up there with a shovel and redirect the water,” says William Simon, a former Berkeley ecology professor who has spent much of the past 15 years leading cleanup projects.

But as these volunteers prepare to tackle the main source of the pollution, the mines themselves, they face an unexpected obstacle—the Clean Water Act. Under federal law, anyone wanting to clean up water flowing from a hard-rock mine must bring it up to the act’s stringent water-quality standards and take responsibility for containing the pollution—forever. Would-be do-gooders become the legal “operators” of abandoned mines like those near Silverton, and therefore liable for their condition.

In mid-October, Senator Mark Udall of Colorado introduced a bill that would allow such “good Samaritans” to obtain, under the Clean Water Act, special mine-cleanup permits that would protect them from some liability. Previous good-Samaritan bills have met opposition from national environmental organizations, including the Sierra Club, the Natural Resources Defense Council, and even the American Bird Conservancy, for whom any weakening of Clean Water Act standards is anathema. Although Udall’s bill is narrower in scope than past proposals, some environmental groups still say the abandoned-mine problem should instead be solved with additional regulation of the mining industry and more federal money for cleanup projects. “If you support cleaning up the environment, why would you support cleaning up something halfway?” asks Natalie Roy, executive director of the Clean Water Network, a coalition of more than 1,250 environmental and other public-interest groups. “It makes no sense.”

Just a few miles from Silverton, in an icy valley creased with avalanche chutes, groundwater burbles out of the long-abandoned Red and Bonita gold mine. Loaded with aluminum, cadmium, and lead, it pours downhill, at 300 gallons a minute, into an alpine stream. The Silverton volunteers aren’t expecting a federal windfall anytime soon—even Superfund-designated mine sites have waited years for cleanup funding, and Udall’s bill has been held up in a Senate committee since last fall. Without a good-Samaritan provision to protect them from liability, they have few choices but to watch the Red and Bonita, and the rest of their local mines, continue to drain.